The invention relates to a method for the combined utilization of residual materials which are fed to the rotary drum kiln in processed form with the raw powder during the production of cement and sulfuric acid according to the so-called Mxc3xcller-Kxc3xchne process and are split off by using chemically reactive carbon which also consists partially of residual materials, at a temperature of over 700xc2x0 C. with the calcium sulfate, whereby the CaO is then calcined at a temperature of over 1,200xc2x0 C. in the presence of SiO2, Al2O3, and Fe2O3 into cement, and the SO2-containing flue gas is freed from dust, washed, mixed with air, and converted to SO3 or H2SO4. The invention relates also to an installation for performing said method which comprises a comminution device for the raw powder components, silos, drying drums, a final comminution device, the raw powder silo, the rotary drum kiln, the burner with burner pipe, the clinker discharge and the cement processor, the flue gas discharge chamber, the deduster, the flue gas washer, and the H2SO4 plant.
The Mxc3xcller-Kxc3xchne process is based on a reducing splitting-off of calcium sulfate at temperatures of over 700xc2x0 C. using carbon. The calcium sulfite, which forms as an intermediary product, reacts with the excess calcium sulfate to form calcium oxide and sulfur dioxide. The cement clinker which forms during the calcination of the CaO essentially consists of tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminate ferrite. The starting material for the classic process consisted essentially of the natural materials anhydride, coke, raw clay, raw sand, gravel, roasting residue, gypsum, and brown coal dust. The moist starting materials were dried, dosed by weight, and then comminuted and mixed in a ball mill. The resulting raw powder is fed into a slightly angled rotary drum kiln and passes through the latter in counterstream to the combustion gas whereby, as a rule, brown coal dust was used. This classic gypsum sulfuric acid process is economically inferior to standard cement production processes. The economy of the process can be improved, however, by utilizing residual materials from other production processes, which are problematic to store. The substitution of the traditional natural raw materials and primary energy medium, that is, brown coal, with suitable residual materials which can be utilized materially and/or energetically is a significant advantage (Chemische Rundschau No. 38, Sep. 24, 1993, p. 11). A great variety of residual materials has been tested, for example, waste gypsum, waste lime, waste sulfuric acid, acid tars, acid resins, brown coal filter ash, construction debris, used porcelains, podsol, and many others. The disadvantage is that the corresponding raw powder components, but also the fuel components, exert a different influence on the process and final products, that is, as well on the cement as on the sulfuric acid and oleum. In addition, this also does not provide for a consistent process control, especially since the following operating stages, such as, for example, dedusting and gas processing, are greatly influenced in their effectivity by the composition of the starting materials.
The invention is thus based on the objective of further developing the Mxc3xcller-Kxc3xchne process and create an installation in a manner so as to enable a further protection of the resources, on the one hand, and landfill space, on the other hand, while observing and meeting environmental regulations and economy.
According to the invention, this objective is realized in that the raw powder components and the fuel components, which include the residual materials to be used, including the compensation and reaction substances required for eliminating components untypical for cement, are stored separately, conditioned, and are then added in accordance with the specified formulation and monitored by way of sampling and sample evaluation; the liquid and solid residual materials to be used as fuel are transported separately to the rotary drum kiln and are then burned with a mutually supportive flame; and the flue gases of the kiln hood and the fuel gas discharge chamber are flash-cooled by feeding in cooling gas.
The incoming residual materials are, like the remaining raw powder and fuel components, stored separately and are then added to the process comminuted and homogenized according to the respective formulation and mixed with each other. The fact that the individual starting products have been previously tested and are also being tested during and following their being mixed, makes it possible to always make available and add a starting product which corresponds exactly to the specified formulation and thus to an optimum process. As needed, compensation and reaction materials are added in order to eliminate components untypical for cement, said materials resulting in a recombustion of trace contaminants, for example, in the rough dust chamber, in order to prevent obstacles in the process further on or problems in regard to the clinker. This ensures a continuously consistent process, even though a great variety of materials and also in changing compositions, are used. By forming corresponding buffers, any difference over time can be compensated, so that, for example, products accumulating in different amounts due to seasonal circumstances can also be available in optimum amounts and can be added accordingly. In addition to large accumulation amounts which, however, also must be combined according to material groups of a similar composition, there are a number of valuable concentration products for CaO, SiO2, Al2O3 and Fe2O3 which are collected and kept available for formulation corrections. By intermediate sampling additional knowledge is obtained which results in possibilities for correcting the raw powder product. An adequate analysis speed hereby can be ensured, in particular in that the analysis method is changed away from molten product to the xe2x80x9cprepared tabletxe2x80x9d. This continuous accompanying analysis makes it possible to advantageously compensate for the high dispersion or band latitude of the starting base of the raw powder. By adjusting the raw powder, the kiln operation and the produced clinker can be made more uniform. This ensures an improvement regarding the certain reproducibility of the clinker, and thus the certain predetermination of the cement quality. The combined addition of the various fuel components into the rotary drum kiln and the partially inter-supporting combustion ensure that a flame which is advantageous for the conversion process is always available. In particular, this also provides the possibility to completely eliminate solid fuel, such as coal, for longer periods and to use, instead, residual fuel materials, such as, for example, wood chips and saw dust saturated with residual materials, ensuring an advantageously uniform flame. The long flame, which is formed, for example, when saw dust is burned, is advantageously supported by the short flame of the solvent and the high-energy and hot flame of the old oil, as well as of the acid tar and acid resin. The flame reaches far into the rotary drum kiln and thus is able to make a safe contribution to an advantageous burning process. The quenching of the flue gases and the fact that the kiln hood and flue gas discharge chamber are sealed advantageously prevents damaging alkali precipitations. In addition, this feeding-in of cooling gas generates a vacuum with an advantageous effect on the entire burning process. This withdrawal of the flue gas manifests itself up to the area of the clinker discharge. The greater amount of flue gas flowing through the rotary drum kiln per time unit ensures optimum combustion of the residual materials. The sealing of the kiln hood hereby ensures that this suction for the flue gas acts far into the rotary drum kiln without drawing in secondary air at wrong places.
According to a useful embodiment of the invention, it is provided that the anhydride content in the raw powder is replaced with 20-100% of residual material. A respective high anhydride content was necessary in the past in order to ensure an operation which was somewhat flawless. Based on the measures according to the invention, this anhydride content can now be reduced advantageously to zero. The same applies to the other components, such as sand, clay, and ferric oxide, which are replaced with power plant furnace ashes, filter dust, etc.
A further improvement of the process can be achieved in that raw powder is added to the flue gas after the same leaves the rotary drum kiln, and in that this raw powder is added only then and with admixture of the dust from the kiln feed. The cold raw powder otherwise forms the condensation point for the hot and sticky starting dust, which then bakes together with the cold dust, and together with it is then added and sticky into the following cyclone of the kiln feed.
The process in its entirety becomes essentially independent from variations in the added products if, as has been provided according to the invention, moist and/or rough and/or hydrocarbon-contaminated mineral starting materials, to the extent necessary, are comminuted, dried, and possibly subjected to pyrolysis, and ground. This provides for the possibility to also safely prepare different starting products to such an extent that they can then be processed according to the process.
According to a useful further development of the invention it is provided that the nozzling in of coal and/or the nozzling in of saw dust saturated with hydrocarbons or similar materials, and/or the nozzling in of sulfuric acid is performed with simultaneous generation of a surrounding combustion mantle created by surrounding lances for liquid fuels, whereby the carbon content is preferably replaced wholly with hydrocarbons and/or other liquid residual materials. By performing the process in this manner, the long flame generated when burning the saw dust is specifically compensated whereby, depending on the number of fuel components used, the individual lines and burners arranged at the end are arranged so as to surround the discharge of the solid fuel pipe or, in particular, are arranged below it, so that a specific influence of the burning out of the saw dust is ensured.
A removal of the metals and alkalis is made possible if the dust enriched with alkali chloride and alkali sulfate is separated into metals, alkalis, and neutral mineral substances also by separate treatment utilizing the paramagnetic effect and returned to the rotary drum kiln while removing the alkalis and metals. The fractionated separation and utilization of the paramagnetic effect also can be extended, if needed, to the other dusts and results in an advantageous, uniform separation and also makes it possible that these products can be reused accordingly. Problematic alkalis and metals are removed.
It is useful that withdrawn odor-intensive, organic products generated during the processes are fed together with primary air to the rotary drum kiln. It is also conceivable that they are fed to so-called biofilters.
In order to avoid dust in the entire process, it is advantageous that the previously fluidized and homogenized raw powder is shaped into pressed parts prior to being fed into the rotary drum kiln. The pressed parts in the rotary drum kiln then advantageously result in a cleaning of the kiln wall, so that the double effect also can be used advantageously for similar processes.
The process is performed with an installation in which the comminution device for the raw powder components and compensation and reaction materials is preceded by separation silos, and in which individual tanks and silos are provided also for the various fuel components and are equipped with a controlled discharge; in which the feed lines for the liquid, gaseous and solid fuel components are surrounded by the burner pipe so as to leave flow channels, whereby the feed lines extend below the solid fuel pipe and discharge into the rotary drum kiln; in which the raw powder feed and the dust discharge of the flue gas discharge chamber are provided with sealing systems; and in which a blow jet cooler is disposed in the flue gas stream behind the flue gas discharge chamber. Depending on the construction of the installation, the individual raw powder components and fuel components can be stored separately and can then be combined according to the optimum process and formulation. This optimum feed material is then further processed in the rotary drum kiln, whereby this is supported in that the combined feeding of the individual fuel components ensures optimum flame formation. The combination burner is constructed so that the solid fuel flame is specifically supported or supplemented by the flames of the other components. The specific vacuum in the flue gas discharge chamber has a double effect on the blow jet cooler, whereby the suction effect is manifested far into the rotary drum kiln.
A corresponding stable construction of the burner pipe is hereby provided in that the feed lines are provided with a mantle pipe in which, in addition to the medium pipe, a blower air pipe and/or a disperser medium pipe are disposed so as to extend parallel to each other. The individual fuel components are thus passed separately into the rotary drum kiln and fed there in such a way that they always can be burned with separate but mutually supportive flame. The individual fuel components are hereby transported in the medium pipe to the burner and are completely and intensively burned, because blower air and, if needed, a dispersion medium, are added parallel or simultaneously. A possible dispersion medium is either steam or compressed air, whereby these materials contribute to the optimum dispersion or distribution of the fuel component, which again results in the specific combustion and complete combustion.
This intensive intermixing of the individual components with the required air and the corresponding division into the smallest possible droplets or components is ensured in particularly in that the mantle pipes of the lines serving as an acid tar line, old oil line, oxygen line, solvent line, accumulated acid line, or viscous oil line are constructed so as to merge with a burner nozzle, whereby the blower air pipe and/or the disperser medium pipe merge into a discharge channel which surrounds the center medium pipe discharge, said discharge channel being formed by the walls of a spin body and an injector cap and discharging at an angle onto the center line of the medium pipe.
In order to be able to utilize the thermal energy in the flue gas, the invention provides that the E-filter associated with the deduster is preceded by a heat exchanger or residual heat boiler which is associated with a blower in the line to the E-filter, and a return blower in the line to the blow jet cooler. Such an association can be accomplished advantageously because the elevated pressure loss via the heat exchanger system is absorbed by the additional blower behind the residual heat boiler. This technical accessory in particular decisively improves the energy utilization balance. The residual heat boiler also provides the condition for an energy station in which the excess steam can be converted into electric energy.
It is useful that the residual water leaving the blow-off tower is further treated, whereby the discharge of the blow-off tower is connected to a 3-stage stirred tank cascade and a chamber filter press or special electrolysis installation with separate separation and extraction of the metals. The special electrolysis installation in particular makes it possible to separate the various accumulating metals separately and extract them, so that they can be made available for smelting again.
The invention is characterized in particular in that it makes available a process and an installation which ensure a significant improvement of the Mxc3xcller-Kxc3xchne process, with regard to process control and safety as well as economy. This makes it possible to add further residual materials to the raw powder as well as to use a great variety of fuel components so that the above mentioned protection of resources, on the one hand, and the protection of landfill space, on the other hand, can be achieved with the necessary safety. It is hereby particularly advantageous that, from an energy standpoint, a largely self-sufficient operation is possible, which also excludes environmental burdens.
Other details and advantages of the object of the invention can be derived from the following description of the corresponding drawing which shows a preferred exemplary embodiment with the necessary details and parts. In the drawing: